This invention relates to a fluidized bed boiler and a high temperature separator used in said boiler and, more particularly, to such a boiler and separator in which the separator has a low resistance and achieves a high separation efficiency.
Current state-of-the-art fluidized bed boilers are not equipped with high-temperature separators for separating the fine particulate material from the gases exiting the boiler. Consequently, a large amount of fine, unreacted materials is blown out of the boiler which results in poor utilization of fuel and sulfur removal agent. For boilers burning fuels with high ash content, this can also cause severe abrasion of the downstream heat-transfer surfaces.
High-speed, or circulating, fluidized bed boilers are equipped with high-temperature separators which capture the flyash and reuse it. The separators are generally of cyclone type, and the flow resistance through the separators at high temperatures is as high as 100-150 mm of water column. As a result, the increase of electricity consumption by the draft fan is equivalent to 4% of fuel cost. This type of separator is difficult to scale up and its efficiency decreases as its capacity increases. Additionally, its structure is complicated and its ash and gas discharge locations are rather localized, which have adverse effects on ash recycle, heat transfer, and the arrangement of convective heat-transfer surfaces.